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Multi-layer glass vs polycarbonate windshields?
I've been researching the history of airline windows and windshields.
Windshields seem to be made out of two types of material. Either multi-layer composite glass or polycarbonate.
I'm wondering what material is more popular on commercial airlines, and has window technology changed over the past 50 or so years on jumbo jets?

Welcome to [aviation.se], please take the [tour]. This place works best on a one question per post basis. While your two questions are related for you, they will get entirely different answers. Please [edit] to ask one question, then feel free to ask the other as a completely separate question.

Not polycarbonate.  Acrylic.  PC is too soft, can't tolerate exposure to gasoline and certain solvents, and scratches if you look at it with a mean face. Windshields are mostly laminated glass, mostly for the hardness, tho some do use acrylic windshields, Pax windows are acrylic (plexiglas). A 1/4 inch thick acrylic pax window has about the same tensile strength as the surrounding ".040 skin.

See also FAA AC 25.775-1 about windows and windshields.


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Load testing a model glider wing
I wish to load test a model glider wing.
The standard static load test methodology using sandbags on the upturned wing would be difficult as the chord of the wing is small - it will be difficult to securely attach the loads required.
Are there any other methods commonly in use to do this kind of test that might be easier?

How much of a chord and span do you have? I have used discrete loads for this in the past (partially filled water bottled suspended at specific span sections).

You can still use some small bags with flour or other soft material inside.
For the wing load test, the bending moment is more critical than the torsion. Therefore, the flour-bags could work fine.
If you want to add torsion and a more precise loading, you can build some sectional fixtures that transfer point loads to the wing.

Thank you. The loads we want to test with are quite high - and there is limited space on the wing. I'm planning to make up some sectional fixtures.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

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Can two opposite localizers to a single runway be on simultaneously?
In case of a single runway with two separate ILS systems (one in each end, facing localizers) operating on two different frequencies, can both localizers be on and transmitting at the same time, or must one be switched off if the other is on?
Please refer to ICAO recommendations if possible.

ICAO Annex 10 Volume 1 has the answer:

3.1.2.7 At those locations where two separate ILS facilities serve opposite ends of a single runway, an interlock shall ensure that only the localizer serving the approach direction in use shall radiate, except where the localizer in operational use is Facility Performance Category I — ILS and no operationally harmful interference results.

In plain language: only one localizer can be on at a time, unless the ILS in use is only CAT I and it has been confirmed that no harmful interference will happen.

Thanks for all but to make sure I understand the answer it is not possible to leave the two ils operating in the same time although the two ils have adifferent frequencies in CAT 2

@user36963 Correct. It doesn't matter that they are on different frequencies, the localizer beams (90 Hz and 150 Hz) may still interfere.

@user36963 I suggest you give Annex 10 a read. There is some additional guidance in Attachment C.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


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What are the failure mode(s) for flying cars in case of power loss?
There seem to be lots of plans (and even some working prototypes) for various autonomous flying cars and flying taxis.
Most of these seem to be based on vertical take-off using some variety of an electric quad-copter (or something very similar).
Conventional planes can glide in the event of engine failure, and traditional single rotor helicopters can auto-rotate. Both techniques should get the aircraft safely (more or less) down assuming the controls remain effective.
What is supposed to happen with a quad-copter based flying car/taxi if the power fails? I don't think the fixed props on a quad copter can auto-rotate, so how are they supposed to land? Ballistic parachutes? or something I've missed?

UPDATE for clarity (I hope). The media seem to use phrases like flying cars/flying taxis and autonomous aircraft or drones almost interchangeably. I'm talking about aircraft that have no (or minimal) wings (and therefore can't glide) and no capacity for auto-rotation. Here are a few examples...

Now have a look at this final photo, it shows an electric aircraft (a glider) with a battery fire. Being a glider the survival options were relatively simple, the pilot landed ASAP and got out of the aircraft. This doesn't seem to be an option for any of the designs I've pictured above.

Does "economic" count as a failure mode for flying car projects as a whole?

Are you asking what the  failure modes are, or about how to fail-safe in the case of power loss?

Failure modes are specific to a particular design. "Flying cars" are (at best) a vaguely defined concept, and each individual design will have its unique failure modes... no wings = no glide option; tiny rotors = no autorotate option; low altitude flight = ineffective ballistic parachute, and etc.

Flying cars as vehicles generally suck because they make crappy aircraft and crappy cars at the same time, almost always combining the worst of the two not the best.

@JohnK Your comment seems to be channeling the original F-111 or the JSF/F-35. evil grin

Well if they tried to make the F111 into a strike aircraft AND a Stryker type vehicle, you'd have something.  A crappy strike aircraft and a crappy armoured vehicle lol.  The main thing with flying cars is the having to make something light enough to fly that can stand up to potholes, curbs, getting dinged by other cars without being grounded.  The objectives are at cross purposes.  In any case, if you have an electric quad copter, why would you want to run it on the road in the first place, except maybe to be able to keep going on a road in bad weather.

Have you followed the efforts of Paul Moller? He's been working on this concept in one form or another for the  last 50 years. Don't know if he is still alive but he was one of my engineering profs in 1975 at UCDavis.

Is your sole question asking about "flying cars" or something else?  Your question is not clear. Sorry, you're apparently allowed to ask about one thing at a time and if additional info of proferred up that is frowned upon.

As I am closely working on some of these projects, I think I can answer.
Let me start from:

if the power fails

this is a rather extreme situation, since everyone is including emergency functionality in case the batteries get below a charge guard level, triggering an emergency landing (still powered).
So to have the "power fails" scenario that your phrasing suggests, you would need a sudden fire or failure of all the battery packs installed on the craft.
What's more likely is that one of the engines will fail, but that's less critical, since all these crafts will have 8 engines as a minimum exactly for this scenario. And once again, this will trigger a powered emergency landing.
Nevertheless, you are right in assuming that these crafts can't autorotate, and some projects are evaluating/have evaluated the inclusion of emergency parachutes similar to the ones seen on some general aviation fixed wing aircraft.

So you are saying a power failure = crash.

@GdD "Emergency landing" != "crash" -- any more than dead sticking a Piper Cub is a "crash".  The landing referred to here is powered and in control (which is the main reason for doubling up the motors).

@ZeissIkon I think that GdD is referring to the case suggested in the question, that I describe as unlikely, where all batteries fail at the same time, making all engines shutoff.

It's a very different scenario @ZeissIkon. A piper cub with total power loss is still controllable, you put it in a field and it isn't a crash, just an incident. An octocopter doesn't typically have control surfaces or a wing, so a power loss (assuming complete loss of electrical power) means loss of all lift and control. It may be unlikely, but it's going to happen at some point.

@GdD by your definition, the only survivable "failure", then, requires deploying a ballistic parachute.  This answer is saying that redundancy is introduced to make "total power loss" so unlikely that the machine is safe to fly in.

It's unlikely that you'll ever be able to build a machine so utterly reliable that failure is impossible, especially while keeping it affordable. In any case the question is what would happen if a power failure did happen, not how it's being made unlikely, and the answer is: "crunch". It's a fair answer, I was simply distilling it down.

@GdD as a counterpoint to yours, there is also to be considered that the certification agencies want to see cold hard numbers on that crash likelihood, and if they are not satisfied, certification is not given.

Note: This answer was for a previous version of the question

What you are asking about seems to be quad-copters, hex-copters, oct-copters.  Flying cars are cars with wings designed for flying and will use airports for takeoff/landing (and gliding down in case of power loss) and driving on roads. See Terrafugia for example.
https://terrafugia.com/

Or this one, with VTOL capability; engine pods rotate forward for aircraft flying mode.

Yes, pilots license is required.
No, the average driver can't afford one - expect something like $250K price tag.
If the flying car loses power, it becomes a poor glider with unknown characteristics at this time.


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Why does the UK CAA medical questionnaire need to know hair colour?
The CAA (UK Civil Aviation Authority) application for a medical certificate asks for hair colour. Why? Are there any diseases / conditions more prevalent to particular colours? Most of the questions are seem to be rooted in common sense, but is hair colour really relevant?

Update in response to comments. Height, weight, sex, eye colour and race ALL have a relevance to medical conditions. Height and weight can indicate BMI and possible eating disorders, many conditions are gender specific, and some medical conditions are more common in different races (Cystic fibrosis is more common amongst northern Europeans, Sickle-cell anaemia is mostly a problem for those with African ancestors). Even eye-colour can (according to google) indicate a increased likeliness of a particular condition.
If hair colour really is there just for general identification purposes, then it's the only question on the form (other than name and CAA reference number) that has no medical purpose.

Definitely not medical reasons so I'm migrating this to Aviation.SE.

FAA medical certificate as well as South African ones also show hair color.

"Why does the UK CAA medical questionnaire need to know hair colour?"-- because they are British.  In America, they need to know hair color.

The same reason they take down your eye color, height, weight, sex, race, etc.  They’re just general stats for identification.

I agree fully with this answer - this has got to be the reason. However, since hair color is as easy to change as hair style, it seems rather pointless as an identifying factor (in any environment) that one could rely on for more than 24 hours...

@FreeMan Except for the bald head.


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What does the orange colored text in a SkyVector route indicate?
If you use a pre-made route in skyvector.com, sometimes there will be orange text.
For example: from KIAD to KTPA with default cruise settings, the second route in the list will have DADES6 in orange.
What does this mean and how would you program these into the FMC?

Green text is an airway, orange text is a SID/STAR.

Thank you J. Hougaard! :)

The Dades 6 is an arrival procedure also known as a STAR (Standard Terminal Arrival Route).
The plate that lists the route and altitudes/speeds for the arrival can be found here.
If you are using a flight simulator, there should be an ARR/DEP page on the FMS that includes (among other things) a list of all the arrivals for the airport you have set as your destination. You can then select the arrival and the appropriate runways.


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Limits on piston-engine power for a given airframe?
I'm looking for an authorative textual source (and indeed any guidance would be useful) on the relationship bewteen a given airframe and the maximum power that it can realistically harness/cope with from a piston powerplant.
For example; if looking at something like a warbird, is there a theoretical way to work out the engine power beyond which the basic airframe design would be unable to cope with the excess torque/force/weight or is it more of an art than a science?
Thank you!

The art comes from balancing dozens of competing objectives and limitations in a series of compromises to produce the final product.  There are just too many variables.

Hanging a different engine is not a simple bolt-on.  There are often other modifications involved, so that raises the question of how much you are willing to modify the airframe, and to get the appropriate analysis and paperwork, to back that up.  Just to give you an idea, here's a turbine c206:  https://www.soloy.com/8203soloy-mkii-turbine-206.html

I assume you mean a single engine? Because a 2-engine design with contra-rotating propellers has way less torque problems. Of course, that's not easily to retrofit to an airframe designed for a single engine, single propeller.

It really depends on how long you want to fly for. Big engines generally require a lot of fuel so dropping a huge power plant on a small airframe may burn through all the fuel you can practically carry fairly fast. But if we assume that you don't want to fly all that long then we run up against the next issue.
You can always try to bolt a merlin engine to a C-150 airframe if you are willing to get creative with your bracket fabrication and perhaps beef up the nose wheel. The issue you will run up against here is at least in part a CG issue. A 1600LB engine on the front of an 800 LB airframe is bound to get interesting. But lets say you move the wings around, and put some ballast in the aft areas to even it out a bit and get a workable CG. You now have nearly 1600 HP up front to have fun with. So what happens?
If you can get this beast to fly you will eventually hit aerodynamic issues depending on the airframe, like Mach Tuck and ultimately at some point you are just going to rip the airframe apart.
So you need to balance structural integrity, aerodynamic stability, CG, the ability to carry enough fuel to actually do something practical and the limits of actually building an aircraft mechanically. There are also practical limits on scaling piston engines in general.

Thank you - that's helpful! Presumably though vibration becomes a serious problem at some point?

@JBronk at some point maybe, but we have gotten pretty good at mitigating that over the years and you could likely mount a lot of engine on a very tiny airframe without issue.

Uh actually there are quite a number of things stopping you from strapping a Merlin engine on a stock C-150, not the least of which is the airframe is probably not going to be able to support the engine weight (the dry weight of the engine exceeds the BEW of a C150!) nor the thrust loads on it without breaking....

@CarloFelicione it was more of a humorous example than a practical one. It would however be an interesting experiment to see how much reinforcement would be needed to pull something like that off.

Another problem that this "super 150" would need to overcome is engine torque.  A F8F Bearcat could not use full throttle on the takeoff roll as the plane would tip over, dragging the wing along the runway.  (Source: Norwood Hansen, WWII pilot  of, and an owner of a Bearcat post-war, now deceased.)  -Skip Miller

I'd be extremely worried about torque adding a Merlin to a C152. More than the CG tbh, as the torque may mean you won't even get off the ground to be troubled by that CG :)

Whatever point the limit is they were at it by the mid 1940s, and went beyond it with lighter, more powerful jets.  Make no mistake about it though, these aircraft had to flown extremely
carefully at low speeds lest the engine/propeller torque become too strong to control.  Jets greatly lessened these issues and offered even higher speeds.
But you may find more happiness in discovering how little power you need to fly.  Try building gliders and then incrementally add power.  You will see there is no point in going anywhere near the "limit" in recreational flying.  You may have an appetite for higher performance for aerobatics or greater speed, but it comes at a cost in weight, fuel consumption, complexity, and risk.
It takes 4x more thrust for a plane to go from 100 to 200mph, 9x more for 300mph, and 16x more for 400mph.  What are your goals?  This is a ladder that can only be safely climbed from the bottom to the top.  But throwing a huge engine on an airframe, as fantastic a garage project as it may seem, would probably be making life a little shorter.
All that said, assuming CG is worked out with counter weights, new engine mount, moving wing, etc., your airframe stress limits are already there in your POH as neg and pos Gs, and Vne.  A larger engine makes it easier to reach Vne, but you can do it with your original in a dive.  But with your heavier re-make, stall and maneuvering speeds will have to be carefully checked, as well as rudder authority in low speed/high power (TakeOff/GoAround) situations. Your new plane will have much better climb performance.
So, this may work out after all by taking a 170/172 engine and putting it on the 150.  I would start by doing some research (so lucky to have the internet).  The Screamin' Sasquatch might give you some ideas.


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How to balance the main rotor of helicopter?
In mi17 class helicopters, the OEM had not given an option of adding weights at main rotor hub or blade tips at unit level. The blade sets are usually static balanced when received by units. Is there any way through which dynamic balancing of rotors can be performed to reduce heavy vibrations without adding extra weights. For eg, either by reducing pitch of heavier blades etc.

When I worked on UH-60 Blackhawks, we used to use a pretty expensive test set to conduct a main rotor track and balance which was pretty involved and took a couple hours to complete just the setup prior to even beginning the process.
I can't remember the name of the system, but it required that we mount a number of accelerometers, which were little chrome cylindrical units about the size of your thumb, to their brackets which were already attached to the airframe in various locations inside the cabin, inside maintenance panels, and were oriented facing in a few different directions in reference to the fuselage's centerline, but always in 90° increments.
Then we removed the avionics nose compartment's airflow inlet screen from the avionics compartment door (basically acts like the hood of a car and opens from the front upwards) to allow for a camera to be mounted in that position. This camera had two lenses, one atop the other, however one of those lenses was actually an IR emitter which was designed to project the specific frequency of IR that the other lense, the actual camera was designed to detect.
The camera was mounted to that compartment door on the precise center lin## Heading ##e of the fuselage facing forward without zero lateral toe angle, but with a pronounced upward angle to ensure the emitter and receiver lenses were centered on a defined station along the main rotor disk. If memory serves that station was about 1' to 2' from the tips of the main rotor blades. On one blade we would affix a strip of specialized reflective tape which was specifically designed to work with IR emitter and sensor camera mounted on the nose and allow the system to "see" how the main rotor disk was tracking.
Once all the required sensors were mounted at their respective locations we would run dedicated cables from each sensor, each accelerometer having a multi-lead cannon plug on the opposite end of the threaded stud used to mount them, to a common location in the forward cabin This process could take some time and wasn't something we would rush, as some of these sensors were mounted in locations which were normally inaccessible when operating, including along the exterior of the aircraft.
There was also a tail rotor camera which mounted to the upper tail pylon and faced towards the spinning tail rotor blades. As with the main rotor, one of the tail rotor paddles would be used to attach a strip of the reflective tape to give the IR emitter something to reflect off of the the camera sensor could detect it. The need to conduct a tail rotor track and balance was not nearly as common as the main rotor track and balance on account of the fully rigid design the Blackhawk was built with. It's amazing how easy and reliable machines can get when you design out most of the moving parts!
Where and how we routed these cables was critical and needed to be done in such a way that ensured that even if multiple attachment fasteners used to secure the cables to the airframe failed, that segment would not come into contact with any parts of the aircraft and cause a safety of flight issue. Yes, for some of the track and balance procedures the aircraft would be placed in an IGE hover, as well as occasionally a short maintenance flight with this test equipment installed and operating.
Once all the accelerometer and camera data cables were run, located in the forward cabin directly behind the pilot seat, usually there was nothing more to install. However there were a couple procedures which were far less common which required that we remove the access panels housing the aircraft's vibration damper assemblies (heavy weights attached to  the airframe with massive flat stainless steel springs) and I believe somehow inhibit their because operation somehow.
Behind the pilot seat where all the data cables were run was the system's brains. Every cable connected to the appropriate cannon plug connector on the face of what was called the Data Acquisition Unit (DAU) which contained the data processing hardware and programming capabilities the system was designed for. Finally a single data cable from the DAU was routed forward towards the pilot seat and connected to an input and display unit which was used as the interface for the maintenance test pilot conducting the track and balance. This unit, really a specialized computer in it's own right, was designed to be handheld or placed on the pilot's lap, but it was NOT small or light. Thinking back it measured about 20" wide, 18" tall, and 3 inches thick, had a small rectangle monochrome LCD display centered at the top of the unit's face, and was equipped with probably a dozen and a half buttons which were the type that are mounted under a single solid piece of textured flexible plastic material with each button outlined, labeled, and slightly raised.
That unit was used to input the specific characteristics of the aircraft, which type of procedure being conducted, which sensors were installed, where on the aircraft they were mounted, when to start measuring, and would provide calculated results after the test procedures, as well as what it reccommended in terms of mechanical adjustments in order to improve the results.
The tests would mostly involve the aircraft being runup to full operational speed, with the system dictating to the pilot how much power to pull in. Once the aircraft was in that configuration the pilot intiated the test on the control unit in his lap, it would collect about a minute or two worth of data, indicate to the pilot when it was finished and satisfied with the data, and the pilot would shut the aircraft down. While waiting for the rotor blades to spin down the system would conduct its calculations and produce the results in terms of "ips", which I never really understood, but more importantly it would also produce a number of different adjustments it reccommended to improve the results as it worked towards a set of results that were all within acceptable standards.
For the main rotor we had two primary means of adjusting the track and balance, vertical primary control (PC) rod adjustments and main rotor blade trailing edge trim tab adjustments. The PC rods were the far easier and less risky adjustments, involving a couple jam nuts, an adjustment tab, and some safety wire, which any adjustments made easily being reversed if needed. Plus the guidance offered by the system was unambiguous and required no special tools or skills. Making adjustments to the rotor blade trim tabs, on the other hand, was anything but clear, required either a large maintenance stand or the removal of the blade, was delicate work with potentially massive implications, and as with any metal reduced the structural integrity of the trim tab every time it was bent for an adjustment.
Usually the maintenance test pilot would run the aircraft up, shut down, read the adjustments reccommended by the system, communicate them directly to the maintenance crew, adjustments were made, rinse and repeat until the system reported the aircraft was within acceptable tolerances.
There were, however, the occasional maintenance test pilots who felt that the reccommended adjustments provided by the system were too aggressive, not aggressive enough, or the results of those adjustments could be achieved through other, better adjustments. Honestly I've seen these guys make a 3 hour process into a 30 minute process and I've seen them make a 3 hour process into a brutal multi-day marathon of insanity. Either way, when if we realized we were working with one of these "I know Best" maintenance test pilots, the mood usually suffered and frustrations were voiced!
This type of procedure and equipment was used back in the late 90's and early 2000's, so they may have a new, lighter, and more powerful system that figures out the adjustments needed in one run. Hope this answers your question at least to some degree.

The system you are referring is vibrex. But any crude way of doing the iteration, if the maintenance crew is not having this equipment and setup? Can we state that, heavier blades should have lesser length of PC so as to reduce drag?


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wake effect on downstream turbine
I want to perform fatigue analysis on downstream turbine blades, but I want to do this analysis with the aerodynamic forces caused by wake effects.Do you have a recommended solver to obtain such data?
I know these ; openfast - turbsim or sowfa but I dont know any knowledge about openfoam.
I can use fluent but the simulation will take too long.

QBlade and nuMAD, if anybody needs this knowledge.

Are these two software the answer to your question? If yes, you can mark it as so


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Lost logbook want to fly again
I took flying lessons in the 1980’s and logged about 50 hours including solos but never got a ppl.  I want to start flying again but after several moves can’t find my pilot logbook.  Do I have any options other than starting over from scratch?

Do any of the following questions provide the information that you're looking for: https://aviation.stackexchange.com/q/767/7532 or https://aviation.stackexchange.com/q/45924/7532 or  https://aviation.stackexchange.com/q/99631/7532

@RalphJ's links are excellent. In particular, https://aviation.stackexchange.com/a/45926/20394 gives some ideas for how to move forward if you wish to reconstruct some (but certainly not all) of your logbook.

A student pilot who hasn't flown in 40 years is starting over from scratch.
Think about what's in that logbook.  Close to zero PIC time.  A handful of expired endorsements.  No current experience.  It has trivial value if you can find it.

Voting down because the pithy "trivial value" claim is simply not true. If the (student) pilot in question already satisfied cross country, certain ground maneuvers, etc... then the logbook could be worth literally thousands of dollars in savings. It depends completely on what was in it and where this pilot is.

@KennSebesta  It's okay to disagree.  As an instructor, I would not credit any of it.  It's the student pilot who brings the experience, not the 40-year-old maneuver logs.

Agreed to disagree. I would be open to crediting all of it on my CFI ticket, pursuant to seeing the pilot's actual (retained) skillset. If this pilot is a flying spouse, and has thousands of hours in the right seat navigating IFR, then I don't need to sit through another cross-country just to satisfy a missing signature. That's very different from someone who had only just barely soloed and hasn't been in the front seat of a car/plane/boat in 40 years. IMO, declaring it has "trivial value" is a decision to be left to Publicola's CFI, and not our random voices on the internet.


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Why is a class 2 medical not valid in Canada?
Upon reviewing the requirements for the Recreational Pilot Permit and Private Pilot License in Canada, I see that only class 1, 3 and 4 medicals are approved.
Are EASA class 2 medicals not valid in Canada at all?

I believe it's only for ATC.  Could be wrong.

The Cat 2 medical in Canada is only for Flight Engineers, Navigators (once upon a time) and Air Traffic Controllers.  https://www.tc.gc.ca/eng/civilaviation/publications/tp13312-2-menu-2331.htm

It would seem that category 2 medicals are different from ICAO class 2. Is the CAR aligned with ICAO regulations here?

Transport Canada has it's own set of medicals for use specifically in Canada. It does not matter what medical you hold elsewhere in the world, to hold a Canadian aviation document/license which is based on your own merit, you require a Category 1, 3, or 4 medical.
The same goes for FAA medicals when trying to get a full unrestricted license which is not based on foreign validation.


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The role of accurate DES FORECASTS for descent planning in VNAV, during the latter stages of an approach
Giving an accurate set of criteria in the “DES FORECASTS” page of the FMC helps produce an accurate descent path.

Typical Descent Profile, Vertical Path
Adjusting the “TAI ON/OFF” (Thermal Anti Ice), “ISA DEV/QNH” and Forecast Winds will produce an accurate path.
If there is a tailwind and a positive ISA deviation, there will be greater track miles required for the descent, and the Top of Descent point will be moved backwards in space to facilitate this longer descent.

Adjusted Descent Profile, Vertical Path, due to changes to the DES Forecast Page
My query revolves around the practical implications of maintaining precise inputs on the “DES FORECASTS” page, especially during the later stages of approach, from FL080 downwards. While managing the descent above FL100 seems more straightforward—options like selecting a higher speed than FMC target speed when in VNAV SPD mode1 with possible speedbrake assistance, or modifying the target speed for a steeper descent profile (assuming VNAV mode over LVL CHANGE or V/S)—the approach phase below FL100 introduces complexities. These include the 250 kt speed limitation, STAR speed restrictions, traffic considerations, and deciding the optimal point for deceleration to a final approach speed of 180 kts (as per ICAO standards).
Given these complexities, does inserting an accurate “DES FORECASTS” page offer tangible benefits during the approach below FL80? In my experience, the pilot monitoring frequently updates the LEGS page. As I understand it, these updates inform the FMC of the actual wind and actual temperature, redrawing the descent profile from that point on. Is this practice of refreshing data for the next active waypoint, and potentially overlooking DES FORECASTS inputs, more critical for ensuring an accurate approach phase?
As opposed to similiar questions asking above the requirement for forecast data to be filled in, this question is trying to understand the forecast page's importance during the latter stages of the approach.
1 FMC Version 14.0+ (common VNAV)

The Descent Forecast page is good, and the descent profile will work better if this has good info in it than if it is blank, but it still has limitations.
First, there are only 3 lines for entering the winds. I've been told (but can't confirm) that the logic is that the FMC uses cruise winds for computations down to the altitude of the first entry, then those entered winds down to the altitude of the second entry, then those winds down to the altitude of the last entry, and then those winds down to the surface.  So picking the altitudes for which you'll enter the winds, matters.  If one were to enter winds at FL 350, FL 310, and FL270 then any significant change in the winds below FL 270 wouldn't be part of the FMC's computations.
On the other hand, I've seen (automated) solutions which enter winds at 15,000', 8,000', and 4,000' -- which is rather useless.  Those entries mean that the FMC constructs the descent path using cruise altitude winds down to 15,000' -- which may reflect reality, but you'd get that logic without any entry at all.  So now the path reflects different winds from 15,000' down, which may or may not include the part of the descent where that accuracy of the path matters most.  And, once you're down at 8,000' and 4,000', every time you hit EXEC for a change to the LEGS page (or any other), the FMC updates the current altitude wind to what it sees "right now," which redraws the path.  (This is why you can see the vertical deviation jump after hitting EXEC -- the path was just redrawn.)
The other major issue with changing winds that the FMC simply doesn't adjust for is that when the headwinds/tailwind component changes, it doesn't just affect your groundspeed.  The FMC uses the wind to figure what the groundspeed will be, and draws the path accordingly, but if you go from 100 knots of tailwind to zero wind, you gain that 100 knots back as indicated airspeed.  Or going from 100 knots of headwind to no wind, you lose energy corresponding to that 100 knots.  And the FMC computations do not account for that gain/loss of energy!
If the change in wind is gradual, like 50 knots over 25,000', you won't see anything drastic while maintaining the idle descent path; maybe maintaining an airspeed slightly above or slightly below the target and never really correcting, but not enough to require much, or any, intervention.  On the other hand, if the wind changes significantly in a short span of time (altitude), then you can easily find your self quite slow (lost headwind) and the power has to come up, or you can see the airspeed going up fairly quickly (lost tailwind or gained headwind), and that may require using speed brakes to hold an airspeed assigned by the arrival (or ATC), or in a really strong shift, to avoid approaching VMO (which should cause a reversion to VNAV SPD before allowing an overspeed -- which protects the clacker, but now you're in VNAV SPD with no protection at all for maintaining the path, and with way too much energy to boot... can you say "high as a kite & getting higher"?).
I've heard of the technique to cope with this of telling the FMC that there is more tailwind than there actually is, which means the constructed path is less steep than it would be, and you have more to work with when the gain in energy happens associated with the loss of the real tailwind.  It's not a technique that I tend to use, but it is out there.
As for ISA deviation, our book says to use the deviation at FL 180.  I don't know to what extent that works better or worse than whatever other altitude might be chosen, and I've not played with it enough to be able to say how much difference it makes in the path to enter it or not.  I'd expect that over enough time & enough flights, any improvement in accuracy of the path will manifest itself has in reduced average fuel burns, so even if the improvement is slight, it's basically free money for the airline, so why not use every tool available?
At some point, I'd expect that FMC's will be optimized to use far more complete wind profiles uplinked from the Dispatch computers, with more granular winds & temperatures, and that would create an even more efficient profile, with fewer times that adding power or drag would be necessary.  It'll take an FMC much more modern than what the 737's have, though -- those boxes are basically 1990's technology with a few upgrades, but the core of the software is so expensive to certify that I doubt it will gain any major leaps in capability.

So when we fly the 737 NG we often don't put in this data under FL080. Unless there is a noticeable change in atmospheric conditions like a strong storm or something through the pilots experience that might make him/her do it. There is little difference in terms of decent performance.
And if for some reason you were unstable or unable to meet speed and altitude constraint because you did not input data in below FL080, you weren't monitoring your aircraft well. and that falls more on piloting ability as apposed to automation. (Unless ATC held you high or fast)

Thank you. But ISA deviation is through the whole descent profile right?


text:
In what scenario would a "climb, crossing climb" or "descend, crossing descend" be issued by a TCAS system?

"CLIMB, CROSSING CLIMB, CLIMB CROSSING CLIMB"
"DESCEND, CROSSING DESCEND, DESCEND CROSSING DESCEND"
(TCAS Aural Alerts - Padpilot, Advanced Instrumentation)

In what situation would a TCAS system advise a climb or descent thorough another aircraft's altitude, rather than issuing a command to climb or descend away from the intruding aircraft's altitude?
FlightGear's (sim) wiki page gives an example of such a command for where the an aircraft at a lower altitude is already is climbing, and/or the aircraft at a higher altitude already is descending. But I struggle fully understand this example, wouldn't the TCAS simply issue a climb command for the descending and a descend command for the climbing as the safer option (granted - there will be inertia lags with the heavy jets). Or rather issue an "INCREASE DESCEND, INCREASE DESCEND" / "INCREASE CLIMB, INCREASE CLIMB." Furthermore, how can the TCAS system presume that descending/climbing aircraft will maintain its rate of descent/climb?

When a TCAS RA is issued, the system first selects the sense (up or down) and then the required strength. During the sense decision, an altitude crossing is avoided if the required vertical separation is sufficient:

The first step is to select the sense (upward or downward avoidance) of the RA. Using
the results of the vertical and horizontal tracking, the logic models the intruder’s path to the CPA.
[...] The
CAS logic computes the predicted vertical separation for each of the two cases and normally selects the
sense, which provides the greater vertical distance.
In the cases where an altitude crossing is projected before the CPA, the CAS logic will pick the sense that
avoids crossing, provided that the resulting vertical distance at CPA is sufficient.
Figure 19 illustrates this case. The desired amount of vertical safe distance (ALIM), varies from 300 to
700 feet, depending on own aircraft’s altitude regime. If ALIM cannot be achieved, a crossing RA will be
issued (see Figure 20). However, delaying mechanisms aim at reducing the incidence of crossing RAs by
deferring an altitude crossing advisory if:

one aircraft is level, or when the two aircraft have vertical rates in opposite senses and they are
separated by at least 600 feet; or
when both aircraft have a vertical rate in the same sense and they are separated by at least 850 feet.

A resolution advisory is altitude crossing if own ACAS aircraft is currently at least 100 feet below or above
the threat aircraft for upward or downward sense advisories, respectively.

(Eurocontrol - ACAS Guide - Airborne Collision Avoidance, emphasis mine)
Figure 20 illustrates the case where the separation for non-crossing (vertical distance at B) is below the minimum desired value (illustrated by the black arrow). In that case, a crossing RA will be issued with "Descend, crossing descend; descend, crossing descend".

You also asked:

Furthermore, how can the TCAS system presume that descending/climbing aircraft will maintain its rate of descent/climb?

The TCAS will always presume that the intruder maintains their current flight profile. This works if the other aircraft does not have TCAS or if the other aircraft is maneuvering such that the vertical separation is even increased.
For crossing RAs, this can however result in a situation, where the other aircraft maneuvers such that the vertical separation is reduced. This will then trigger a modified RA:

Subsequent advisories
During the course of the encounter, the RA strength is evaluated every second. Occasionally, the threat
aircraft will manoeuvre vertically in a manner that thwarts the effectiveness of the issued RA. In these
cases, the initial RA will be modified to either increase the strength or reverse the sense of the initial RA
(when the initially issued RA is no longer predicted to provide sufficient vertical spacing).
[...] Figure 23 shows an encounter where an
initial Climb RA requires reversal to a Descend RA after the threat aircraft manoeuvres.

(Eurocontrol - ACAS Guide - Airborne Collision Avoidance)

Something tells me that when you hear the voice of TCAS speaking and it adds "NOW", as in figure 23, the pulse rates in the cockpit increase quite noticeably.


text:
Do ICAO rules allow a pilot to level-off during a descent to comply with the 10,000 ft speed restriction?
I understand under FAA rules in the NAS a pilot may level-off during a descent, without additional coordination, to comply with the 250KIAS below 10,000’ speed restriction…

(AIM 4-4-10) …”If it is necessary to level off at an intermediate altitude during climb or descent, advise ATC, except when leveling off at 10,000 feet MSL on descent, or 2,500 feet above airport elevation (prior to entering a Class C or Class D surface area), when required for speed reduction.” && “NOTE - Leveling off at 10,000 feet MSL on descent or 2,500 feet above airport elevation (prior to entering a Class C or Class D surface area) to comply with 14 CFR Section 91.117 airspeed restrictions is commonplace. Controllers anticipate this action and plan accordingly. Leveling off at any other time on climb or descent may seriously affect air traffic handling by ATC. Consequently, it is imperative that pilots make every effort to fulfill the above expected actions to aid ATC in safely handling and expediting traffic.”

Is this same allowance codified anywhere in ICAO/EASA rules? Thanks for the help!

Welcome to Aviation.SE!

Is any temporary leveling-off actually explicitly forbidden other than it "may seriously affect air traffic handling by ATC"?

At least in the AIM…I read this as prescriptive, which is located just prior to the quote in my question, “If at anytime the pilot is unable to climb or descend at a rate of at least 500 feet a minute, advise ATC.”

No, this allowance is not codified in ICAO or EASA regulations, however, in practise the note from your quote is equally applicable here.

authors: Vladimir F Героям слава


text:
How do I update my name on a Canadian Aviation Document Booklet?
I am a holder of a Canadian Aviation Document Booklet, however have since legally changed my name and now need to request an ADB with my new name.
The official guidance on updating or renewing only deals with updates to earned licenses and ratings, and the only relevant form is the Application for an Aviation Document Booklet that doesn't have any language relating to applying for an ADB with information that differs from a previously issued one. I can't seem to find any official guidance from Transport Canada at all on what to do in this case.
Do I just submit the application form with the relevant new information (e.g. name, sex) changed? What supporting documentation do I need to provide?

Per an email response to my inquiry from Transport Canada: (strikethrough mine, see below)

Please complete the following form (Flight Crew Licensing Declaration of Name) and submit via email to aviation.ont@tc.gc.ca, along with the required supporting documentation, Apply for a pilot permit or licence (tc.gc.ca).
If you would like your ADB to be re-issued afterward, please include this request in your email as well as the $35 replacement fee receipt.
Payment can be made online here, Online Payment System - Canada.ca (tc.gc.ca).

Edit: After further clarification from Transport Canada the correct way to get an ADB with your new name after submitting the Declaration of Name form is applying for a new ADB following the process on their website.
The required supporting documentation is mentioned on the form itself:

I understand that before further change in my name can be made for licensing purposes, I must submit proof of change of name from the Government of the
Province in which I am residing at this time.

The gender change section of the form simply states "Attach supporting documentation" so it's unclear what's required for that.
Note that aviation.ont@tc.gc.ca is the email for the Ontario Regional Service Centre  - For other regions of Canada the correct contact can be found on this page.


text:
Is the Centre of Gravity moved by an aircraft travelling at “High Speeds”?
The following quote is from G. Bristol’s book, Ace the Technical Piloting Interview:

[The] movement of the centre of gravity is due to a change in weight. The distribution of the aircraft’s weight can change for three reasons and thus cause the centre of gravity to move. The three reasons for a change in aircraft’s weight are:

Fuel Burn
Passenger Movement
High Speeds*

*Note. This is so because the greater the speed, the greater the lift created. To maintain straight and level, the aircraft adopts a more nose-down attitude, accomplished by creating lift at the tailplane. This lift effectively reduces the weight of the tailplane section of the aircraft.

I was surprised to read that the centre of gravity (CG) changes with “High Speeds.” As I understand it, the horizontal stabiliser produces a downwards force to counteract the moment about the CG produced by lift acting through the centre of pressure.
Though the adoption of a nose down attitude at higher speeds to maintain straight and level does make sense due to the increased speed (assuming constant $ \rho $).
But I am still struggling with the sentence, “This lift effectively reduces the weight of the tailplane section.” I just can’t see how speed could change the actual CG.
Does the actual CG change at “High Speeds”?
(Though I do understand that aerodynamics is universal to all aircraft, if there are differences in discussion between light aircraft compared to turboprops and passenger jets, I would prefer the discussion to be more towards the latter, thank you)

Perhaps more grammer than physics " reason for a change " implies moving CG to re-balance it with aerodynamic forces.  Moving crew was commonly done in airships for trimming.

@RobertDiGiovanni If nothing else, the sentence "this lift effectively reduces the weight of the tailplane section of the aircraft" is a non-sequitur even though trimming is sometimes done by mass redistribution.  It is a non-sequitur because the center of gravity is determined by actual weight,  which does not change as a result of aerodynamic forces on the tailplane.

As a technicality, anything which applies a force to the aircraft can cause bending, which would move the CG.  It would surprise me if drag forces from high speed move it significantly, but technically it does have an effect.

@CortAmmon This would be yet another way to answer the question posed by the title without addressing the issues tedioustortoise is asking about in the body of the question. No doubt someone will soon point out that if the airplane ls moving along at high speeds, then so is its CG.

@sdenham and that would be why it was a comment rather than an answer.

@CortAmmon Indeed, which is why I wrote "would be"... I may have become oversensitive to anything that might be read as suggesting that the argument quoted in the question is in any way reasonable.

Changing the aerodynamic forces on any part of the aircraft CANNOT change the distribution of mass within the aircraft structure. The center of mass, (AKA center of gravity) can ONLY be changed by moving mass around within the structure, (or adding/removing mass), and remains constant unless you do that. Aerodynamics does not (CANNOT) have anything to do with it.  It doesn't even change if you move the airplane to another planet, or out into space, in free fall, where there is "no" gravity.

Now although this may only confuse the basic point here, it is true
that if you do something that requires redistribution of mass (be it
fuel, cargo, passengers, whatever) then that mass redistribution,
(if/when it occurs), will change the CG, nevertheless, it is
mass redistribution, and only mass distribution, that can directly cause
a change in the CG.
Any action you take that requires or necessitates mass redistribution
cannot by itself change the CG.

This gets my vote for best answer, but may I propose a rephrasing of the last paragraph, which I had to re-read? I think what you are saying is something like "True, if you do something that actually redistributes mass, then you may change the CG, but even if an action you take creates a need to redistribute mass, it does not mean that the action has itself changed the CG." My apologies if I am not being clear or have misunderstood your intent here.

"aerodynamic forces […] CANNOT change the […] aircraft structure." - well, they could, by breaking the aircraft apart :)

Hah! yes, on that point, you are correct.

@sdenham, No actually, I meant exactly what I wrote. If you word it the way you suggest, you would be conflating the two things.  How can you "Do something that   actually redistributes mass ..." without redistributing mass ?  Examples abound and are mentioned in some of the other answers, but in all cases, it is the actual mass distribution (if/when it occurs), that changes the CG, not the action that necessitates the mass redistribution.

@CharlesBretana Clearly my attempt at rephrasing failed in my goal to be unambiguous, but I feel there is a concern here. Maybe it's just me, but when I first read that last clause, I thought someone might disagree thus: "but if you did something that necessitated mass redistribution (in a way that changes the CG), then that first action caused the  GC change". This would be a valid use of 'cause', and the chain of causality is often important (e.g. in accident analysis), but it is clear from the passage quoted in the question that this is not what the book's author is talking about...

@CharlesBretana ...WRT "if you do something that requires redistribution of mass ... then that mass redistribution will change the CG": mass redistribution does not necessarily change the CG, even though it may well do so. I thought you were pointing out that only mass redistribution can change the CG (putting aside asymmetrical changes to the gravitational field!), and so, to change the CG, you actually (as in 'nothing else will suffice') have to redistribute mass. Clearly, my proposed change utterly failed to make anything clear!

@sdenham,  I'm not sure if I am reading your comment accurately, but if you are speaking from the perspective that the chain of causality must include connections that only exist due to a human's intentions, then semantically, you might be correct, but, the point of analysis is to isolate the direct cause of effects, not the indirect causes that are five, or three, or even only one connection away... This, I believe, is true especially when the intermediate connections are not absolutely required, but must require some other independent event to occur to make the connection.

As to your comment "mass redistribution does not necessarily change the CG", well, technically that is true, you could, by sheer chance, move the mass around in such a way so that the resultant CG ends up exactly where it was, but that would a fluke (and dependent on the stated tolerances to your definition of "exact"). I did not see the need to break out this exception... (as I did not see the need to state clearly, every time I use the phrase "mass distribution", that this also includes the addition and/or removal of mass.)

@CharlesBretana Human agency is not an issue here; the hypothetical response "but if you did something that necessitated mass redistribution (in a way that changes the CG), then that first action caused the GC change" would be a valid chain of causality even if both actions  were performed by automatic machinery. What I am trying to say here is that if someone responded to your final phrase with this thought, they might go on to think that the passage quoted in the question is correct after all. As far as I can tell, that would not be a conclusion you support (quite the opposite, in fact!)

You may not think there is any real risk of anyone thinking that way (but see Koyovis's reply...), and it is up to you whether you think I am making an issue out of nothing. WRT mass transfer without CG movement, one can seek to do it quite deliberately, as in drawing fuel from both left and right tanks. As it is clear what you mean here, this is not an issue that I would have mentioned, except that it is the first part of a sentence that I felt could be misunderstood... To be clear, I strongly support your answer as being the correct one.

I may be misunderstanding the point you are trying to make (it is getting a bit convoluted), but if I understand you, I am quibbling because to my mind, there cannot be any such action that "necessitates" a mass distribution. And unless the actual mass distribution is an absolutely unavoidable, physical consequence of the first action (and I cannot think of any first action that could be described such), then the first action cannot be argued to be a direct cause of the change in CG.

As to Koyovis answer, yes, it is true that when an aircraft goes supersonic, the center of pressure changes (moves aft), and this shift changes the trim forces and, everything working as designed, a fix is to transfer fuel and case a CG change. But using this type of logic, you could equivalently argue that a pilot's decision to fly to a destination further away (which would permit supersonic  flight) causes a change in the CG.   Or, you could argue that a patient having a medical issue while supersonic that necessitates an early landing for medical treatment causes a CG change.

I mean you are probably aware of the theory (argument) that the flapping of a butterfly's wings can completely change the weather on the other side of the globe at some point in the future. Yes, everything is connected in a chain of indirect causality. That is why it is so important to emphasize clarity in direct causes of effects. Otherwise, we are forced to make a decision as to where (when) in the infinite chain of past events, we are going to stop. I remember a story told about a fly, and a bird, and a cat, and a dog, and a horse and a general on the horse, and a battle, and a war....

I'd suggest that while this answer is correct it discusses mass, while the text quoted by the OP discusses weight- in an uncomfortably vague fashion. At the very least I'd expect somebody responding to such a question in a technical interview to consider the possibility that "weight" in this context included aerodynamic contributions.

To @sdenham's point, that last paragraph is a mouthful...  Yes, I completely understand the point you are making, but had to read it a few times, and ultimately I don't think it adds any value or clarity to the first paragraph.  CG is only affected if you redistribute mass.  Period.

I took the OPs reference to weight instead of mass as nothing more than than the ubiquitous misstatement or misuse of terms or mis-identification of weight for what is actually mass. In no way would I ever assume that a reference to weight is intended to include aerodynamic forces.  Weight is simply the force of gravity on an object in a gravitational field equal to the mass times the strength of the field is local units of acceleration.

@Michael Hall, Yes, in hindsight, I agree with your reaction to my last paragraph. As I believe removing it completely would make all these comments confusing, I will edit it to make your point clear.

@CharlesBretana What work are you quoting in your answer?

The author of the book makes a correct introduction: "..movement of the centre of gravity is due to a change in weight. The distribution of the aircraft’s weight can change for three reasons". The footnote is incorrect: a change in tailplane lift never causes a shift in Centre of Gravity. Aerodynamics have no business with gravity forces acting on mass - CoG does not change according to tail plane trim, the Centre of Lift does.
Image source, earlier mentioned in this answer.
But there is a mitigating factor, in case of fuel transfer. Modern passenger planes do change CoG by re-distributing fuel when cruising, exactly for purpose of reduced drag from positive tail plane lift. For instance in the A380, by means of the trim fuel tanks in the horizontal tail.
Image source
The other case where shifting the CoG helps efficiency at high speeds, is of course for supersonic aircraft. Wing CoL shifts from about quarter wing chord at subsonic speeds, to half wing chord at supersonic speeds. Fuel transfer around transsonic speed then shifts the CoG aft as well, to prevent large trim drag.

Re A380 -- see footnote in my answer.  PS was typing reference Concorde url independently before seeing your not-yet-posted answer--

I think it's better to say the tail is lifting for trim, not  so much longitudinal stability, which would be more of a transient case.  If the tail is lifting for trim, it must mean the net pitching moment of the aircraft, absent the tail, has reversed from nose down to nose up, even with the wing operating at some positive angle of attack, correct?

@JohnK The tail is lifting for trim indeed. Longitudinal stability must always be maintained though, which in cruise is no problem with a lifting tail.

While this answers the question posed by the title, it does not help with the issue actually being raised here, which is whether the quoted passage is correct - and it is not, a fact that is clarified by its author's note, which leaves no doubt that he is fundamentally confused. @tedioustortoise presumably wants the latter to be addressed, and was unaware that the title allows for an answer which avoids that issue. In retrospect, perhaps a better phrasing would be "Do the aerodynamic forces on the tailplane contribute to determining the location of the center of gravity?"

@sdenham Perhaps the CG is considered an "effective" CG, and relates to trim drag, not longitudinal stability per se.  As AOA goes down with increasing speed, pitching moment goes down, and trimming forces required to regulate that target AOA go down.  For the purpose of trim drag, it's as if you moved the CG aft, offloading the tail, and maybe that's what they are really talking about.  Ideally you'd want the tail to be completely unloaded for trim at cruising AOA, with its lifting forces only contributing to longitudinal static stability,

@JohnK I won't go into details of why the author's way of looking at the issue is not just useless but confusing - and probably incoherent - even if you call it an "effective CG", because the more germane point here is that the question tedioustortoise wants answered is not answered by noting that trim tanks are used in some aircraft.

@Koyovis Indeed; the answer could be tightened up considerably by deleting everything else.

Aerodynamic forces on the tailplane contribute to determining the [CoL (+1) and therefor its relationship with the] location of the center of gravity, which you need to account for "To maintain straight and level".

@sdenham as per suggestion.

Perhaps also change "The other case where CoG shifts at high speeds ..." to "The other case where shifting the CoG helps efficiency at high speeds ...".  It's something real jets do in practice, but it is optional.  The whole question is about whether speed directly affects CoG, rather than just motivating you to change it by other means, so unambiguous wording is good whenever possible.

(I made a suggested edit with that change, but I didn't find great wording for the new end of that paragraph; could use improvement.)

NO.
The "center of gravity" is where the total weight of the body, or alternatively it is total mass, may be thought to be concentrated.
It is often seen as the internal physical feature of the solid body and (as commonly understood) is not altered by velocity, acceleration or density of the surrounding environment. It may be altered only by altering the internal structure of the physical body, like relocating some mass differently inside it. Hence, for the aircraft, only moving any mass in, out or relocating inside would change it. Fuel burning and passenger movement are cases for that but change of velocity is not.

I have removed the thinking what the author possibly wanted to say.

There are two separate issues here.
Firstly, as long as we are not physically redistributing the mass of the aircraft, then a change in the aircraft's pitching tendencies, as speed is varied, absolutely should not be described as a "movement of the centre of gravity... due to a change in weight."  So the quoted text is unambiguously in error.
The second issue concerns whether or not the horizontal tail actually develops more upward lift, or less downward lift, as cruise speed is increased.  The quoted passage suggests that this is necessary to keep the aircraft's nose down to keep the wing meeting the air at the increasingly small angle-of-attack that is associated with increasingly higher airspeeds.  And there's no doubt that the wing's angle-of-attack must indeed be decreased as the airspeed is increased.
But the truth is that due to the nose-down pitching moment from the cambered wing, which may be expressed as a pitching coefficient, the tail typically must produce more downforce or less upforce in higher-speed cruise than in lower-speed cruise.  Despite the fact that the elevator is positioned lower at higher airspeeds (in the simple case where the whole stab itself is not moveable for trimming the aircraft.)  This seeming discrepancy can be accounted for by the fact that the aircraft as a whole flies at a lower pitch attitude and angle-of-attack in high-speed cruise than in low-speed cruise, and this affects the angle-of-attack of the horizontal tail.  So it is a mistake to imagine that the tail effectively seems to "get lighter" as airspeed is increased.  The opposite is actually true, if we are intending to describe the combined effects of the actual weight of the tail, and whatever upforce or downforce it must generate to trim the aircraft.
It is the case that during supersonic cruise, an aircraft's overall center of lift can move quite far aft, which in the absence of a change of C.G., would have to be compensated for by a strong nose-up change in pitch control trim.  In the Concorde, this is handled by pumping fuel aft during acceleration to high-speed cruise.  But similar procedures are not normally used on aircraft that cruise firmly in the subsonic range.1
So in summary, the quoted passage is riddled with errors.
Footnotes:

Quote from a PDF on Airbus A380 fuel system:  "Center of Gravity (CG) Control Transfers: CG control transfers maintain the aircraft's CG forward of the aft certified limit by transferring fuel from the trim tank to the appropriate wing tanks. There are no aft CG transfers, because the CG only has a minor impact on the cruise performance. "  Source: "FUEL SYSTEM OF AIRBUS A380 AIRCRAFT SYSTEMS MOHAMAD HAMDI NAJJAR Faculty Number: 363215016", https://pdfcoffee.com/fuel-system-of-airbus-a380-aircraft-systems-pdf-free.html

The logic of "*Note. This is so because the greater the speed, the greater the lift created. To maintain straight and level, the aircraft adopts a more nose-down attitude, accomplished by creating lift at the tailplane. This lift effectively reduces the weight of the tailplane section of the aircraft." is so circular and utterly flawed.  The author is claiming that A) the wing angle-of-attack, and therefore aircraft pitch attitude, needs to be lower/ more nose-down at high speed (true).  ...

(Ctd) B) the tail need to produce more upward lift to accomplish this (my answer argues that this is false, but for the sake of argument, let's pretend that it is true.)  C) Since the tail is supposedly doing what it needs to do to keep everything balanced, we've now created a problem, similar to a shift in CG-- and the plane is no longer in balance.  (Makes no sense whatsoever.)

You should not rely on Mr. Bristol's book to ace the Technical Piloting Interview. He makes three errors in the quoted section:

Mass is not weight. The mass of something can only be changed by adding or taking away stuff. Weight is a force, the product of mass and acceleration. For the nitpickers: Yes, mass does increase once you reach a substantial fraction of the speed of light, but we can comfortably neglect this relativistic effect in aviation.
The center of gravity does not change when weight changes from, say, a change in acceleration. The turning airplane is not only subject to gravitational acceleration, but also to inertial acceleration resulting from its movement on a curved path. Change the curvature of the path and weight changes, but the mass does not. Now it can be argued whether gravitational and inertial mass are two distinct things, but so far nobody could demonstrate any difference between them, apart from semantics.
The gravest error is the third one: Tail load becomes more negative as speed increases when the wing has positive camber. Since the center of pressure moves back on a cambered wing as angle of attack decreases, the lift distribution between wing and tail (or canard) must change in order to keep the center of pressure of the full airplane at the center of gravity.

When a symmetric airfoil is used on the wing, the tail load will stay constant over angle of attack if we only look at the aerodynamic forces. But powered airplanes also produce thrust, and an offset thrust line will also affect the pitching moment. When engines are mounted below the wings and drag rises with airspeed above minimum drag speed, more thrust is needed to balance drag and will add to the engines' pitch-up contribution. This requires more lift on the tail, too! Only very high engine placements (like on the Lake amphibians or an Ekranoplan) will cause tail lift to decrease (or downforce to increase) when speed rises near the airplane's top speed.

Is it normal to talk about "weight" in terms of forces other than gravity?  (In the non-inertial reference frame of a turning airplane, you're considering centrifugal force part of the weight?)  With my non-aviation physics background, I'd have said weight = m g, and the atmosphere is thin enough that g is close enough to the same 9.81m/s^2 everywhere you can fly a plane on Earth.  (And certainly not varying with time enough to matter.)  Other forces acting on the mass of the plane are obviously significant and need to be accounted for somehow, of course.

@PeterCordes If you think how the effects of a load factor >1 on a pilot are described: Yes. If you make a distinction between gravitational and inertial weight: No, but that is approaching scholastics.


text:
Aircraft zones - what is meant by zone 999?
There are designated zones where Positions/FINs are allocated - so components have both Part Numbers, Serial Numbers, Positions (or FINs for Airbus) and Zone classifications.
Does zone 999 refer to being "un-zoned" or "unclassified"? Or something else perhaps? Is this only concerning Airbus this or is it universal across all manufacturers?

Figure: Excerpt from Airbus -  a330 of the Electrical Routing ATA 24-92-02-34B

The ATA-100 specification states zones numbered in the 9xx range are "Reserved for uncommon differences between aircraft types not covered by standard series numbers."


text:
What is the time derivative of the angle of attack?
Suppose a flying missile's velocity vector has components $u, v, w$, as illustrated below.

From my knowledge of flight dynamics, the angle of attack is
$$\alpha = \arctan \left(\frac{w}{u}\right)$$
where $u, w$ are time-varying. Then,
$$\frac{d\alpha}{dt} = \frac{1}{1+\frac{w^2}{u^2}} \left(\frac{w}{u}\right)'= \frac{w'u - wu'}{u^2+w^2}$$
Some books indicate
$$\frac{d\alpha}{dt} = q + \frac{Z}{mu}$$
where $q$ is the second component of angular velocity, $Z$ is the third component of the total force, and $m$ is the mass of missile. How can these two formulas be the same?

They are two equations describing two different states.
The first equation is the momentary state of $w$ and $u$ without regards as to what causes variation of $w$ and $u$.
The second equation is the change in angle of attack as an inertial response to a force or moment acting on the missile.

I get the idea but how could we derive the second equation explicitly?

Assuming that there isn't an error in the books you've read:
Both formulas are true. It's true that
$$\frac{d\alpha}{dt} = \frac{w'u - wu'}{u^2 + w^2},$$
and it's also true that
$$\frac{d\alpha}{dt}= q + \frac{Z}{mu}.$$
From this, we can conclude that
$$\frac{w'u - wu'}{u^2 + w^2} = q + \frac{Z}{mu}.$$
Both of these two formulas describe the way that the angle of attack changes, but they describe it in different ways.
I'm not sure exactly how the $q + Z/mu$ formula was derived, but it seems to be related to the fact that angle of attack is related to pitch and the flight path. Specifically, for flight with zero bank angle, the angle of attack is the pitch angle minus the climb angle. It looks like the $q$ term comes from the rate of change of pitch, and the $Z/mu$ term comes from the rate of change of climb angle.

Yes, I believe they are both true but how can we formulate from one to another? I don't understand how to derive formula 2

@Dat I added another paragraph describing my best guess about the $q + Z/mu$ formula.

I see, I understood the q term but still can't get the Z/mu term. The second formula is from https://en.wikipedia.org/wiki/Flight_dynamics_(fixed-wing_aircraft)

First we can use the definitions of w, u, alpha, and beta to define
$$ \frac{w}{u} = \tan\alpha $$
$$ u = Vcos(\alpha)cos(\beta)  $$
Now lets look closer at the first equation you provided using the definitions above:
$$\frac{d\alpha}{dt}  = \frac{1}{1+\frac{w^2}{u^2}} \left(\frac{w'}{u}-\frac{u'w}{u^2}\right) = \frac{1}{1+\tan^2\alpha} \left(\frac{w'}{V\cos\alpha\cos\beta}-\frac{u'\tan\alpha}{V\cos\alpha\cos\beta}\right)  $$
Which can be simplified further with trig identities to
$$\frac{d\alpha}{dt} = \frac{\cos(\alpha)w'-\sin(\alpha )u'}{V\cos\beta} $$
We can see that we're on the right track here, using first-order approximations, w'/V is approximately q and u'/m is approximately Z (by Newton's second law). From the sines and cosines we can tell that pitch rate on its own is only a valid approximation while alpha is small.
Why The Term For Z?
Why is force included here?  Because angle of attack and pitch are measured in different frames and a change in airspeed could cause you to overestimate or underestimate the new angle of attack. This isn't novel or particular to the case of missiles, as a similar equation appears in Real-Time Aerodynamic Parameter Estimation without Air Flow Angle Measurements by Eugene Morelli, and I've seen similar kinematic equations used in avionics.
Let's draw what happens graphically:

From the image we see that while flight path is changing, pitch angle changes alone won't account for all the differences.  We also have to account for a change in flight path angle relative to the airmass, which can be approximated using the component of flight path change that's perpendicular to the flight path.  If we assume angle of attack is small or that Z is perpendicular to the flight path instead of to the body, this rotation equals arctan(Z_w/ (m*V)).
Further derivation with fewer approximations
Now the piece omitted in other answers.  The kinematic equations of motion as shwon in Morelli, et al:
$$ w' = q u-p v + g*a_z+g\cos\phi\cos\theta $$
$$ u' =  r v - q w + g a_x + g \sin\theta $$
Plugging in the definitions for u,v, and w as function of V, alpha, and beta into these equations and then inserting those into our formula for the derivative of alpha gives (see Morelli, et al. for more information)
$$\frac{d\alpha}{dt} = q + p\sin\beta + \frac{g}{V}\left(-\sin\alpha\left(a_x-sin\theta\right)+\cos\alpha\left(a_z+\cos\phi\cos\theta\right)\right) $$
Note that even though we used calculus and trig identities, not kinematics to get this equation, it matches the expected rotation matrix for angular rates between the body frame and the wind frame, using this example, or also this question:
$$ \begin{bmatrix} \delta \phi \\ \delta \alpha \\ \delta \beta  \end{bmatrix}=
 M_{a,b2w} \begin{bmatrix} \delta p \\ \delta q \\ \delta r  \end{bmatrix}  $$
$$ M_{a,b2w} = \begin{bmatrix}
 \cos\alpha\cos\beta & \sin\beta & 0 \\
 -\cos\alpha\sin\beta & \cos\beta & 0 \\
 \sin\alpha & 0 & 1 \\
 \end{bmatrix} $$
We can convert those pesky accelerations (well, pesky if you're not trying to measure them, then they're really handy) and include gravity in the total force:
$$  T_{f,z}/m =  g \left(-\sin\alpha\left(a_x-sin\theta\right)+\cos\alpha\left(a_z+\cos\phi\cos\theta\right)\right) $$
And we get:
$$\frac{d\alpha}{dt} = q - p\sin\beta + \frac{T_{f,z}}{m V} $$
So with some generous assumptions that sideslip and roll rates are small so p*sin(beta)≈0, that Z includes gravity already, and that Z is mostly aligned perpendicular to the incoming wind, this equals your original formula, we've shown that
$$\frac{d\alpha}{dt} \approx q + \frac{T_{f,z}}{m V} $$
Variables used
p,q,r = roll, pitch and yaw rates in the body frame
ϕ,α,β = roll, angle of attack, and sideslip angles
u,v,w = Components of aircraft velocity along the body longitudinal, lateral, and normal directions
ϕ,θ = Roll and pitch in the inertial frame
V = Total velocity, vector sum of u,v,w
T_fz = Total force perpendicular to the flight path, pointing in opposite direction of angle of attack
m = Aircraft mass
References:

Eugene A. Morelli, Real-Time Aerodynamic Parameter Estimation without Air Flow Angle Measurements

I think the equations are not referred to the same axys.
The first equation refers to the angle of attack, the angle between both components of the velocity refered to the body axys (x along the body), using a non-inertial frame (as moves with the missile) . Well, actually following some comments, is not actually the angle of attack, it will be the angle of attack in the specific case of v=0.
The second equations looks to be referring to the rotation of the missile referred to an inertial frame of an external observer (for example, Earth), so actually, it looks like the actual movement of the body frame refered to that observer in a specific rotation component .
Imagine an example, that I am able to provide the right thurst to the missile in such a way that I keep u, w and q constant rotating in a circle.
In this case, the angle of attack will be constant and its increase 0 with time but the second alpha will be increasing/decrasing with a constant increase/decrease, also this change will be linked to the circle rotation.
I think you can also make the math and relate both equations (you will need more components!) taking care of inertial forces.
Final comment, as you are introducing as well a second term in teh second alpha equation, it really looks that it is an specific case in the movement of missile.


text:
For slow-flying ultralights, how would a delta wing compare to a biplane layout of equal wing area?
Context: By "slow-flying" I refer to ultralights that can be classed as  "motorfloaters" - similar wing loading to a hang-glider, stall speed below 40km/h, cruise speed not much above.
I'm interested in designing something of similar capabilities to M. Sandlin's Bloop ( http://m-sandlin.info/bloop/bloop.htm ) where the plan is to get into the air as cheaply as possible and then "fly too slowly/lightly to really be able to hurt yourself". (See also Ron Wheeler's Skyscout, more traditional ultralight design but manages an empty weight of 55kg, MTOW 135kg and a stalling speed of 32km/h, and and first flew in 1974 - http://all-aero.com/index.php/54-planes-p-q-e-r-s/9873-skycraft-scout- .)
The Bloop's designer chose a biplane layout as an easy way to achieve high wing area and structural strength for a given span, with cheap/light materials. The wings are approx 9m^2 each, with a span of 7.6m. (Due to diminishing aerodynamic returns on additional wings, I'm not sure whether to treat this as a total wing area of 18m^2m, or less - I have seen some sites suggest *1.5 instead of *2 as a good estimator.)
Given deltas also offer a large wing area and good structural strength, I am curious: Assuming similar wing construction - rigid metal frame, foam LE supports, stiff fabric covering - what differences in flight performance could be expected if an otherwise-similar craft flew with a single delta wing, of equal total area but lesser span? For example's sake, let's say a span of 5m.
Off the bat, I would expect induced drag to be much higher due to vastly lower aspect ratio, but I'm unsure to what degree that may be balanced by the removal of an extra wing's worth of profile drag, interference between the two wings, and parasite drag from struts and bracing wires etc. Plus, possible improvements in lift coefficient for same AoA range as I would think the wing would operate at much higher Reynolds numbers due to greater average chord length.

In all honesty there are a lot of questions in here. Furthermore you seem to be concerned with the structure and rib design when you should be wondering if a slender wing will fly at all at the speeds you can expect of an ultralight. If you can refine this down a bit or at least make clear what is the main question, you'll get a better response. Meanwhile, look into the effect of wingspan on lift to get an idea on why cropped deltas are usually high-speed propositions.

You mean the sort of wing on a flexwing microlight like this:  https://en.wikipedia.org/wiki/Ultralight_trike#/media/File:AirBorne_XT912_Tourer_microlight.jpg

You should clarify whether you're referring to a Rogallo-derived wing, as on classic "delta" hang gliders, or a rigid delta wing like a Voorhees or Dyke Delta homebuilt aircraft.  They're very different in terms of flying characteristics.

@AEhere Thanks, I've edited as you suggested.

@ZeissIkon Yes, apologies, I've amended my question to specify a rigid, non-Rogallo wing. The Verhees Delta is very similar in appearance to what I'm picturing, but this would be far lighter (120-130kg MTOW) and with a tiny paramotor-class engine (8-15kW range) whereas the Verhees is more of a "proper aeroplane". :)

One major issue with a delta wing was discovered in the early days of supersonic fighters: delta wings don't handle well at low speeds.  At high angle of attack, they (like any highly swept planform) exhibit strong "Dutch roll" in which roll and yaw are coupled in an oscillation, and because they stall at very high angles of attack the Dutch roll comes on when control authority is at its lowest.
Your plan, to fly just above the stall at very light wing loading, will require control surfaces that make up a very large percentage of the total wing area, effectively compromising lifting area.  You'll also need a very large vertical fin to maintain stability, and much/most of that will need to be movable for yaw control.
Generally, the main reason Rogallo-derived designs have maintained dominance in hang gliders is because they overcome most of these failings of rigid deltas, and can be made lighter, store more compactly, and cost less to construct as well.

That's interesting and a shame - I've found deltas my preferred planform for slow-speed in RC flying, but I guess it's one of those things that vary with scale. :( What are the characteristics of the non-rigid, Rogallo-style deltas that help minimize these issues? I know very little about behaviour of non-rigid wings.

@ThomasBullock That's an interesting question; you may want to see if you can turn it into a fully formed question on this site.  This site doesn't work like forums, where one question can lead to another and be answered right there.  Instead, it asks that we ask one solid question at a time, when then gathers a bunch of answers.  Follow-on questions are meant to be separate.  This helps keep things focused, and especially helps internet searchers who may ask the same question as you.

@WayneConrad Thanks. New here, and, as you guessed, more used to forums! I'll make a separate question.

@Thomas - the main factor I've found (also with models) to improve stability of deltas is that the fin needs to extend well behind the trailing edge of the wing. This would cause a problem on a full size aircraft, as you already need an excessively long nose gear to achieve enough AOA to take off.

The main (low speed) characteristic of a delta is that when it stalls, the lift doesn't drop sharply. Instead the drag continues to rise, and with enough power you can fly at extremely high angles of attack. With the power off, you can descend very steeply, with the nose high and very little airspeed.
This is a lot of fun in a model with enough power to accelerate vertically out of a stall, but in a microlight it would be just as dangerous as a normal stall.
A side effect of this is that landings often result in large flare angles, and take off require more angle than for a conventional plane. This means you need very long landing gear, and the pilot's view may be restricted.

"and the pilot's view may be restricted" Hence the Concorde's droop nose, if I'm not mistaken.


text:
What's this outlet of IAE V2500 for?
Anybody knows what is this outlet for and why it is designed in such way?

Edit: On MD-90 didn't see such thingy

Why is the question dwon-voted? always I don't expect any up-vote but for down-vote it could be better to tell us the reason.

The picture of the MD-90 engine shows the exact same drain mast (see under the IAE logo)!?

@Bianfable Thank you for posting that nice answer. I'm not sure if it's the answer because the engine in that question is different but I guess you're right and that's the answer. Then I think it's better that an expert approves it or If you sure, please post your answer. lets not to close this question. this engine is different than that one.

@Bianfable Aren't the engine designers the designer of nacelles? Why are they different? Do the aircraft designers design the nacelles?

No the OEM designs the nacelles in close collaboration with the engine builder or builders.  Those types of protrusions are almost always fluid drains of some kind, or vents were fluid can also potentially exit, intended to keep fluid discharge in the freestream so it doesn't collect and flow along the skin.


text:
What licenses should I get for the (flight) equipments that I want to make?
For making and selling all equipments of aircrafts what or which licenses should I get? and from where? Will I be able to sell them all around the world?
Edit: This question is different than this one. One of them is for a new equipment and another is to modify them. It looks they need different licenses. Please vote to reopen it.

Please explain your research effort so far and clarify exactly which doubt you have

@expeditedescent I even don't know from which office or organization should I start. Which one is in charge!? Please vote to reopen the question. see the edition.

This question is WAY too broad.  ("All equipment... all around the world"?!)  What country are you in?  Start there, with whatever aviation authority exists, then expand.

Might I suggest researching Title 14 of the US Code of Federal Regulations. It would be a good start. It is a very long read and very general. But, your question is too broad to narrow an answer down any further. For more detail, edit your question to include country, aircraft category, class and type, product type, product use, etc.


text:
Why do the aircraft made by the Soviet Union have fans in their cockpits?
Surely the countries which were a part of the Soviet Union were not so hot then why are there fans in their cockpits? e.g. TU-134

or IL-76

or AN-124

It keeps the Russian pilots from sticking their heads out the window to feel the breeze.

Because air conditioning was too expensive.

@A.I.Breveleri, I don't think you can have a pressurization system without ability to control temperature, or that it would be any cheaper, so for pressurized aircraft—and all the pictured ones are—the air conditioning is ‘free’, because it is already included in the pressurization system.


text:
How can an airplane fly with single propeller without rolling over?
I have no knowledge about aviation or mechanics or something. Recently I started a computer game 'besiege', a kind of sandbox-like game with bunch of parts to make all kinds of machinery.
And I'm trying to make a single-propeller airplane. What I'm concerned about is that it might roll over. I made a simple helicopter once before, which rotated to the other direction of the way propeller(of course facing up) did when only one prop is attached. I know this is why another small prop is at the tail.
So, is my airplane going to stay in balance with single propeller? I considered putting one on another rotating to the opposite direction in the same speed too, but that isn't the way I am planning to. Thanks in advance.

When it is slow, the two or three wheels should keep it from flipping over.
Once it is fast enough to fly, the wing will provide what we engineers call roll damping: Any tendency to roll† will cause an opposing moment which will stop the motion quickly. The rest is done by a differential deflection of the ailerons, so the wing creates an equal and opposite rolling moment to that of the propeller.
What is roll damping: Once the wing starts to roll, one side will go up while the other goes down. This will cause a change in local angle of attack and, consequently, local lift. The down-moving wing will see a higher angle of attack and a local lift increase, and the opposite happens on the other side. Total lift will remain unchanged, but now the change in the spanwise lift distribution will lift the down-moving wing back up and vice versa. The movement stops before it could pick up any speed.
With powerful engines, engine torque is a real problem and needs to be canceled with a few tricks:

Camber on the vertical tail: The vertical tail will create a side force and rolling moment which depends on the speed of the air flowing over the vertical. This helps to make the correction depend on the power setting of the engine. Just make sure that the vertical is in the slipstream of the propeller.
With contra-rotating propellers you can cancel the rolling moment of each propeller with that of the other. This needs a more complex gearbox, however.
In operation, apply power changes only slowly. With its narrow undercarriage, the Me-109 would become uncontrollable if the pilot went from idle to full power on the ground too quickly.
Watch the gyro forces of a spinning propeller: In taildraggers, the aircraft will yaw due to gyro forces once the tail is lifted during the ground run or the pitch attitude is changed in flight. Also, yawing (rotation around the vertical axis) will create a pitch moment (which acts around the spanwise axis).

† Roll: Movement around the longitudinal axis.

"The Me-109 would become uncontrollable if the pilot went from idle to full power on the ground too quickly" - I love the use of the word uncontrollable to describe being upside down and on fire :p

Plenty of WWII-era aircraft, especially the late war ones tended to have such massive torque that go-arounds on short final were discouraged due to loss-of-control risks.

@JonStory: Upside down and on fire would be a rather extreme outcome. Normally what happened was that the aircraft yawed left and went into whatever happened to be there. If the take-off was on a wide open field (remember, many airfields were round grassy patches back then), the normal result was less spectacular.

An aircraft has control surfaces for controlling its attitude: elevators for pitch, ailerons for roll and rudder for yaw.
At flying speed, the ailerons can provide much more torque than the propeller and the rudder can provide more torque than the p-factor and the effect of the rotating slipstream, so the aircraft simply flies straight with ailerons and rudder slightly deflected, with the amount of deflection depending on the engine power.
On the ground, wheel steering or asymmetrical braking is used to compensate the yaw below the speed at which rudder becomes effective and roll stability is ensured simply by the main gear track width.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Lockheed SR-71 take off protocol
I'm intrigued by the Lockheed SR-71's take-off procedure, as it seems different to that of civilian aircraft. I would like to know what are the major differences in take-off procedure, and why?
For example, most aircraft begin to take off like the following: engine one on, warming up. Engine two on, warming up, etc. But is this the same for the SR-71 what was its take-off protocol?

Are you asking about takeoff? Your example sounds like just engine start.

No as in, did they warm it up did they take off immediately, did they have to check weight, did they have to do the calculations of (weight fuel and cargo).

Can you, if possible, provide a link to or more in depth description of the procedures in question. This question is a bit vague but I feel it can be honed into a solid question.

I recommend this book, it really goes into more detail than anything else: Flying the SR-71 Blackbird: In the Cockpit on a Secret Operational Mission  http://www.amazon.com/Flying-SR-71-Blackbird-Cockpit-Operational/dp/0760332398

If you are referencing the manuals found here the procedures look pretty standard to me. Granted they involve some thing specific to the plane they are generally what one would find. Pages 2-19 through 2-23 seems to cover the start up procedure and it looks pretty standard. Make sure ground unit is connected, check fuel flow, check engine is open, start, check RMP (provides some trouble shooting for RPM issues as well). It also goes on to say left engine first for odd flights and right engine first for even flights to keep the wear some what in line. There are a lot of "Note" sections but you are talking about one of if not the highest performance aircraft ever made so these are to be expected.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Can you identify those parts (sensors), on test aircraft and the purpose?
I have seen many photos with those sensors attached to the test aircraft, Can you provide why they are used and what do they measure?

Here is another example on SuperJet:

The "rope" helps reduce the static on test aircrafts so the testing sensors and instruments work more precise. The "spike" is a long pitot tube, which measures the pressure way before the airplanes body starts changing it (you can see this for high speed planes too, where the mass of air they push in front of them would have a significant impact on a pressure measured close to the aircrafts body). A quick Google search can help a lot to get more information.

On the super jet that's a pitot tube rather large but still it's a testing aircraft. Aircraft's use pitot tubes to measure airspeed. The example, from an Airbus A380, combines a pitot tube (right) with a static port and an angle-of-attack vane (left). Air-flow is right to left. A pitot (/ˈpiːtoʊ/ PEE-toh) tube is a pressure measurement instrument used to measure fluid flow velocity. And so on, The basic pitot tube consists of a tube pointing directly into the fluid flow. As this tube contains fluid, a pressure can be measured; the moving fluid is brought to rest (stagnates) as there is no outlet to allow flow to continue. This pressure is the stagnation pressure of the fluid, also known as the total pressure or (particularly in aviation) the pitot pressure. Go here, for evidence.

Question is why it's so special on the test aircraft? Do they compare readings with standard tubes on the side of fuselage to know corrections for the position error? Otherwise long tubing can introduce errors like delays ect.

Yes, They do compare The "long" pitot tubes to the normal length'd one, Why is it so special to test on aircraft? Well (No offence) You should know that people are always trying to make bigger, better aircraft " Do they compare readings with standard tubes on the side of fuselage to know corrections for the position error?" Yes they do Quite often, Hope that's answered your Question.


text:
How are change-overs between regional air traffic patterns communicated?
The airport near me that has two major landing/takeoff patterns part of a large regional air traffic control plan involving other major international airports (SFO/OAK/SJC)
The duplicate-cited question addresses the general question of change-over. I am in need of public service information on when this change happens.  I have edited this question to remove the general curiosity.
Generally  I would like to know how  the changes between two regional plans  is communicated or published to the public or if it is available on a public service. Specifically, the East-Plan/West-Plan change in the SFO/OAK/SJC area (CA, USA)

90% of the time the take off direction is in direction that does not impact me.
When the prevailing winds change the takeoff pattern is directly overhead. This has an impact on alarms and equipment. In order to automate the shutdown of certain equipment I would like to monitor regional ATC information.  I have considered simply monitoring flight patterns, prevailing winds, and weather conditions. A definitive source is preferred because it takes some time to reconfigure the equipment.  Does such a ATC or FAA source exist for the general public?

@fooot I need to monitor the traffic change in order to turn off sensitive equipment, I have removed the "general curiosity" and made the question more specific. I do not believe it is now a duplicate

You could look into D-ATIS. It’s the ATIS info in digital form that could be parsed for runway usage. I know you can access it from Foreflight, but I don’t know if it’s transmitted in the open or not.

There won't be any publicly available source for what you're looking for. Any information that you could get access to (as mentioned below) won't be reliable enough to predict when the runway changes will occur. The initial coordination always happen over secured phone lines between the controllers at the radar approach/center facilities and towers. There is no way you can hear this.
Each airports ATIS (Automated Terminal Information Service) (https://en.wikipedia.org/wiki/Automatic_terminal_information_service) will be reporting what the runway(s) in use are - but this won't actually change until the runway change becomes active, maybe 5 minutes before. I suppose it would be possible to monitor this, probably via LiveATC (or setting up your own equivalent). You could somehow monitor or export this information and listen for key words to trigger your whatever-you're-using-to-shut-off-your-"sensitive equpiment" - but I think you'd get a lot of false positives. On the same note, you could also hear controllers making their initial calls to pilots advising them of the impending runway change (probably on arrival feeder sectors of ATC or the center descent clearances).
I don't think either of these methods are reliable enough for what you're looking to do. You may consider moving your "sensitive equipment" to somewhere not near an airport.

Best bet might be for the OP to call NorCal TRACON and ask if there is anything that is publicly accessible that does show impending changes to the flow.  The FAA website has a fair amount of real-time info, although I don't think airport departure/arrival flows are there (but I could be wrong).  If the OP can talk to the right person at NorCal, they may be aware of some method, possible specific to their facility, that the OP could use to get longer than 5-10 minutes notice.  I would take something pretty obscure, though.

A few years back I had a problem with electric trains impacting a sensitive magnetic test, we could tell directly the local electric rails active hours that showed up as noise  and had to measure at night . Urban environments have their challenges , thanks for the reference. For this time it's a house alarm so moving it defeats it's  purpose ;)

@RalphJ - I highly doubt anyone answering the phone at NorCal is going to care about the OPs request. I'm not trying to sound rude, but they just aren't going to care. What's available is what's available. There is real time information available via some of the commercial tracking sites, but nothing like the OP is asking for. Delays and maybe current flow restrictions/delays, and that's really about it. Internally, sure, we have all sorts of goodies. We aren't giving away the keys to the kingdom...